The Prius Prime is a dual fuel vehicle, able to run 100% on Electric, or 100% on gasoline, or a computerized blend in-between. This presents me a great opportunity to be able to do a direct comparison with the same car of an EV engine vs an ICE engine.
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Toyota computer claims 3.2mi-per-kwhr.
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Kill-a-watt (https://en.wikipedia.org/wiki/Kill_A_Watt) claims 2.2mi-per-kwhr.
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Additional 1.5% losses should be assumed in the wires if you wish. (120V drops down to 118V during charging, meaning 2V of the energy was lost due to the resistance of my home’s wires).
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Level 1 charger at home (known to be less efficient).
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Toyota computer claims 53miles-per-gallon (American Gallon).
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I have not independently verified the gallon usage of my car.
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295 miles driven total, sometimes EV, sometimes Gasoline, sometimes both.
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30F to 40F (-1C to 4.5C) in my area this past week.
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Winter-blend fuel.
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12.5miles per $electricity-dollar (17.1c / kw-hr home charging costs)
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17.1 miles per $gasoline-dollar ($3.10 per gallon last fillup).
If anyone has questions about my tests. The main takeaway is that L1 charging is so low in efficiency that gasoline in my area is cheaper than electricity. Obviously the price of gasoline and electricity varies significantly area-to-area, so feel free to use my numbers to calculate / simulate the costs in your area.
There is also substantial losses of efficiency due to cold weather, that is well acknowledged by the EV community. The Prius Prime (and most other EVs) will turn on a heater to keep the battery conditioned in the winter, spending precious electricity on battery-conditioning rather than miles. Gasoline engines do not have this problem and remain as efficient in the winter.
I don’t expect gas to be so much cheaper than electricity
This will vary fairly widely based on electricity pricing in your area, and ambient temperatures. Batteries are less efficient in cold weather, and have to maintain minimum temperatures.
Here in AZ for instance, we pay about 13 cents, and temperatures are usually warmer than in OP’s use case. If you’re in an area that tends to have higher gas prices or prices that swing up and down a lot that will also have a fairly large effect on the comparison for you.
Pricing should be more stable than gas overall though either way since electricity pricing is usually pretty stable for the consumer, outside of Texas that is.
The /c/technology discussion also brought up many examples of nighttime charge / time of use electric plans.
Depending on your country or other locations, you might have substantial savings for night time off peak savings.
I can drop from 17.1c to 12c night time / off-peak charging for example. But my on peak / daytime charge skyrockets to 28c.